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Dual-action disposable clamp

Dual-action disposable clamp description/claims

This application claims priority from U.S. Provisional Patent Application No. 60/849,515 entitled “DUAL-ACTION DISPOSABLE CLAMP” filed on Oct. 5, 2006; U.S. Provisional Patent Application No. 60/857,700 entitled “DUAL-ACTION DISPOSABLE CLAMP” filed on Nov. 8, 2006; and U.S. Provisional Patent Application No. 60/901,171 entitled “DUAL-ACTION DISPOSABLE CLAMP WITH CLUTCH NUT” filed on Feb. 13, 2007, which are each hereby incorporated by reference in their entirety.

The present invention relates to a temporary fastener, and more specifically to a disposable clamp.

Modern aircraft are manufactured from numerous panels and other parts that are fastened together with rivets, screws, bolts, and other permanent fasteners. To aid in assembly, parts are typically held together with temporary clamps and fixtures until permanent fasteners can be installed. Parts that incorporate sealant on the mating surfaces require that the temporary clamps exert sufficient force to squeeze excessive sealant from the joint while pulling parts together before the sealant fully cures. Heavy structures fastened with 5/16″-size permanent fasteners, for example, require in excess of 500 pounds clamp load to squeeze the sealant out to an acceptable thickness and hold the components together. Other applications, such as in wing-to-body joints, require upwards of 1500 pounds with 5/16″-size fasteners to temporarily secure components. The clamp load requirements for other sizes are generally proportional to the cross-sectional area of the basic fastener diameter.

Blind hole clamps are desirable for airframe assembly, because their installation and removal can be more easily automated than the installation and removal of conventional bolts and nuts. However, existing blind hole clamps do not have a blind head large enough to avoid surface damage on the blind side panel when high clamp loads are imparted.

Oftentimes, one or more work pieces are joined with clamps to maintain part orientation during an autoclave curing cycle. Threaded-type reusable blind clamps are capable of high clamp loads, but lack the smooth shank needed to avoid clogging with resin as the parts are cured. As a result, the clamps are difficult to remove and may damage the work pieces upon removal. Blind tack rivets may have the required smooth shank but are incapable of imparting sufficient clamp load to maintain parts in the required orientation. Conventional slave bolts are not capable of automated installation and removal.

In addition, threaded temporary blind clamps are easily clogged with sealant and resins, making removal from assemblies difficult and necessitating cleaning before they may be reused. Another problem with threaded temporary fasteners is that they protrude above the accessable panel surface by a relatively large amount. Accordingly, robotic assembly equipment must retract or back away from each panel to avoid collisions with installed clamps. As a result, installation of threaded temporary fasteners requires additional time to traverse from one location to another.

Finally, the clamping capability of threaded temporary clamps is limited, because the blind head is discontinuous and high clamp loads result in surface damage to the work pieces. Temporary blind tack rivets have a low profile but must be removed by drilling through the manufactured head. Drilling through the head, however, generates metal chips that frequently damages panel surfaces. Oftentimes, for example, the rivet spins in the hole during the drilling operation, halting the advance of the drill bit through the tack rivet and prolonging the removal cycle time. Tack rivets also have very low clamp loads and produce a blind-side upset that is not suitable for use in laminated composite panels.

Slave bolts may consist of a conventional nut and bolt or a pull-type lock bolt with a swage collar. Slave bolts may provide a non-clogging shank, non-drill out removal and high clamp loads. However, slave bolts require access to both sides of the work pieces and, in many cases, two operators to install. Two-sided installations are difficult and costly to automate.

Therefore, a need exists for a clamp, or a temporary fastener, having a smooth cylindrical shank without grooves, threads and other discontinuities that may become clogged with sealant or cured resin and which is capable of high clamp loads (greater than 500 pounds for a 5/16″ size clamp) without damaging fragile panel surfaces. In addition, a need exists for a low profile temporary clamping fastener capable of installation and removal from a single accessible side of the work pieces, preferably by robotic equipment, in a manner that does not generate drilling debris. A one-sided installation and removal process is desired for saving labor costs over a conventional two-person operation using nuts and bolts. Finally, a need exists for a temporary fastener having a predetermined geometry to control installation clamp loads rather than allowing the installation force to be controlled by outside influences, such as, operator skill.

A clamp may having a core bolt in threaded engagement with an expander is provided. The clamp may have a smooth shank positioned between the expander and a wrenching end of the core bolt. The shank may have an integral flange adjacent the fracturing at a predetermined compression load. The core bolt may have a first and a second break groove capable of fracturing at predetermined compression loads. A spacer may be engaged with the shank to prevent rotation of the shank during installation of the clamp. A nut may optionally be provided. The nut may be in threaded engagement with the core bolt and may rotate with the core bolt during installation.

Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:

FIGS. 1A, 1B and 1C illustrate a side view, a perspective view, and a cross-sectional view along line A-A of a clamp in an embodiment of the present invention.

FIGS. 2A, 2B and 2C illustrate a side view, a perspective view, and a cross-sectional view along line B-B of the clamp of FIGS. 1A-1C at least partially installed in a work piece in an embodiment of the present invention.

FIGS. 3A, 3B and 3C illustrate a side view, a perspective view and a cross-sectional view along line C-C of the clamp of FIGS. 1A-1C in an installed condition in an embodiment of the present invention.

• Provisional Patent
• Utility Patent

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